Dual braking system for a mining locomotive

ABSTRACT

The braking system includes mechanically actuated apparatus to move the brake shoes into frictional engagement with the locomotive wheels. The mechanically actuated apparatus has a hand wheel suitably mounted in the operator&#39;&#39;s compartment. The hand wheel is connected to one end of a rotatable screw device. The other end of the rotatable screw device is threadedly secured in a threaded bore of a bracket member. The bracket member is secured to a transversely extending equalizer bar. The equalizer bar is connected by a pair of link members to vertically extending brake levers through a lost motion connection. The vertically extending brake levers are pivotally secured to wheel brake assemblies that include a pair of depending hanger levers to which brake shoes are pivotally connected. The brake assembly includes a wear adjustment device to adjust the position of the brake shoes due to wear. Rotation of the hand wheel moves the bracket and equalizer bar longitudinally and through the link members pivots the vertically extending brake levers. The brake levers, in turn, move the brake shoes into frictional engagement with the wheels of the locomotive and apply a braking force thereto. The fluid actuated auxiliary braking apparatus includes a manually operated hydraulic pump in the operator&#39;&#39;s compartment connected to a source of hydraulic fluid. The actuating shaft of the pump has a hand wheel connected thereto. One or more piston cylinder servomechanisms are mounted on the locomotive adjacent the equalizer bar with the piston rod connected thereto through suitable overtravel linkages. The ports of the hydraulic pumps are connected by conduits to the cylinder on opposite sides of the piston within the cylinder. Rotation of the hand wheel connected to the hydraulic pump in one direction supplies fluid to the piston cylinder assembly to extend the piston rod and move the equlizer bar. Movement of the equalizer bar moves the brake shoes into frictional engagement with the locomotive wheels through the same linkages associated with the mechanically actuated apparatus. The rotation of the hand wheel connected to the pump in the opposite direction moves the brake shoes out of frictional engagement with the locomotive wheels. The amount of frictional force exerted by the brake shoes when actuated by the fluid actuated auxiliary braking system may be easily, accurately and positively controlled.

United States Patent [191 Shoemaker [11] 3,750,852 [451 Aug. 7, 1973 DUAL BRAKING SYSTEM FOR A MINING LOCOMOTIVE 75] Inventor: Leon H. Shoemaker, Russell, Ky.

[73] Assignee: National Mine Service Company, Pittsburgh, Pa.

[22] Filed: Oct. 29, 1971 [21] Appl. No.: 193,655

Primary Examiner-Duane A. Reger Attorney-Stanley J. Price, Jr.

[57] ABSTRACT The braking system includes mechanically actuated apparatusto move the brake shoes into frictional'engage ment with the locomotive wheels. The mechanically actuated apparatus has a hand wheel suitably mounted in the operator's compartment. The hand wheel is connected to one end of a rotatable screw device. The other end of therotatable screw device is threadedly secured in a threaded bore of a bracket member. The bracket member is secured to a transversely extending equaliZe r baEThe equalizer bar is connected by a pair of link members to vertically extending brake levers through a lost motion connection. The vertically extending brake levers'are pivotally secured to wheel brake assemblies that include a pair of depending hanger levers to which brake shoes are pivotally connected. The brake assembly includes a wear adjustment device to adjust the position of the brake shoes due to wear. Rotation of the hand wheel moves the bracket and equalizer bar longitudinally and through the link members pivots the vertically extending brake levers. The brake levers, in turn, move the brake shoes into frictional engagement with the wheels of the locomotive and apply a braking force thereto. The fluid actuated auxiliary braking apparatus includes a manually operated hydraulic pump in the operators compartment connected to a source of hydraulic fluid. The actuating shaft of the pump has a hand wheel connected thereto. One or more piston cylinder servomechanisms are mounted on the locomotive adjacent the equalizer bar with the piston rod connected thereto through suitable overtravel linkages. The ports of the hydraulic pumps are connected by conduits to the cylinder on opposite sides of the piston within the cylinder. Rotation of the hand wheel connected to the hydraulic pump in one direction supplies fluid to the piston cylinder assembly to extend the piston rod and move the equlizer bar. Movement of the equalizer bar moves the brake shoes into frictional engagement with thelocomotive wheels through the same linkages associated with the mechanically actuated apparatus. The rotation of the hand wheel connected to the pump in the opposite direction moves the brake shoes out of frictional engagement with the locomotive wheels. The amount of frictional force exerted by the brake shoes when actuated by the fluid actuated auxiliary braking system may be easily, accurately and positively controlled.

9 Claims, 7 Drawing Figures PATENTED AUG 7 I975 SHEET 0F 4 vow DUAL BRAKING SYSTEM FOR A MINING LOCOMOTIVE BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a manually operated fluid actuated braking apparatus and more particularly to a dual braking apparatus for a mine locomotive that includes a mechanical brake actuator and a fluid brake actuator.

2. Description of the Prior Art Conventional mine locomotives have mechanically actuated braking systems in which a telescoping screw is attached to the hand wheel and to an equalizer bar. Rotation of the hand wheel moves the equalizer bar which, in turn, through mechanical linkages to the brake shoes moves the brake shoes outwardly against the wheels.

Fluid actuated locomotive type brakes are also known, as illustrated in US. Pat. Nos. 2,274,021, 2,406,440, 2,657,771, 2,762,459 and 2,970,674. Fluid actuated braking systems alone have inhernet disadvantages as, for example, loss of fluid pressure by conduit failure and the like during the braking operation and also loss of fluid pressure while the brakes are engaged and the locomotive is parked. US. Pat. No. 2,657,771 provides a separate mechanically actuated parking brake on the locomotive. A separate complex lever system is associated with the mechanical parking brake and both brake systems are independent of each other.

A mechanically actuated braking system has a substantial number of disadvantages as the sole braking system for the locomotive. Because of the mechanical linkages, accurate braking control is difficult and substantial effort is required to exert braking force to the brake shoes, especially at high speeds. There is a need for a braking system that has the advantageous features of a mechanical braking system that is operable to override an auxiliary braking system and to positively engage the brakes while the locomotive is parked and an auxiliary fluid actuated braking mechanism that is operable to apply the locomotive brakes through the same linkage system with a minimum effort by the operator. Further, there is a need for a locomotive braking system that provides accurate control of the braking force at different locomotive speeds.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a dual braking system for a mine locomotive that includes an equalizer bar extending transversely across the body of a mine locomotive. The equalizer bar has end portions that terminate adjacent to wheels mounted on the sides of the mine locomotive body. Brake shoe assemblies that include brake shoes are positioned adjacent to the wheels. A pair of brake levers are pivotally connected to the brake shoe assemblies and are arranged to pivot in one direction and move the brake shoes into frictional engagement with the wheels. There are also provided links connecting the pair of brake levers to the equalizer bar end portion. A mechanical brake actuating means is operable to mechanically move the equalizer bar and, through the links, pivot the brake levers. A fluid actuated brake actuating means that includes piston cylinder means is connected to the brake assemblies and is operable upon actuation to move the brake shoes into frictional engagement with the wheels. Overtravel means are provided for both the mechanical brake actuating means and the fluid actuated brake actuating means. The overtravel' means permit either the mechanical brake actuating means or the fluid actuated brake actuating means to frictionally engage the brake shoes to the wheels.

The fluid actuated brake actuating means is an auxiliary braking apparatus that may be connected to existing mine locomotives having a mechanical brake actuating means. The auxiliary braking apparatus includes a closed loop hydrualic circuit that has a manually operable fluid pump, a fluid reservoir, piston cylinder means, and conduit means connecting the fluid reservoir to the manually operable fluid pump and connecting the manually operable fluid pump to the piston cylinder means. The manually operable fluid pump is ar ranged upon actuation to supply fluid through the conduit means to the piston cylinder means to extend or retract the piston cylinder means. The piston cylinder means is arranged to be connected to a portion of the existing mechanical brake actuating means so that upon actuation of the manually operable pump the piston cylinder means actuates the brakes connected to the mechanical actuating means.

With this arrangement it is now possible to provide dual brakes for a mine locomotive without major modifications to the existing mechanical braking apparatus. The fluid actuated brake actuating means is arranged to operate the same brake shoes as the mechanical brake actuating means. There are provided, however,

two separate systems, either of which is capable of applying the brakes regardless of the position of the other. It is preferred that the fluid actuated brake actuating means be normally employed as the service brake during the operation of the mine locomotive and the mechanical brake actuating means be employed for parking and emergency use.

Accordingly, the principal object of this invention is to provide auxiliary braking apparatus that may be conneeted to an existing mine locomotive having mechanical brake actuating means.

Anotherobject of this invention :is to provide an auxiliary fluid actuated brake actuating means that operates the same brake shoes as the mechanical brake actuating means.

These and other objects and advantages of this invention will be more completely disclosed and described in the following specification, the accompanying drawings and the appended claims.

BREIF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a mine locomotive illustrating the dual braking system wherein a pair of actuating cylinders are connected to the brake arms on opposite sides of the locomotive.

FIG. 2 is a view in side elevation of the locomotive with the dual braking system thereon illustrated in FIG. 1. i

FIG. 3 is a fragmentary top plan view of another embodiment of the invention where a single fluid actuating cylinder. is connected to the equalizer bar along the longitudinal axis of the locomotive.

FIG. 4 is a viewin side elevation of the embodiment illustrated in FIG. 3.

FIG. 5 is a top plan view of another embodiment of the dual braking system where a pair of actuating piston cylinder assemblies are connected to separate braking levers that are, in turn, connected to the brake shoes.

FIG. 6 is a view in side elevation of the embodiment illustrated in FIG. 5.

FIG. 7 is a schematic illustration of the closed loop I hydraulic circuit for the manually operated fluid actuated brake.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 there is illustrated schematically a rail mounted mine locomotive generally designated by the numeral 10 that has an operators compartment 12 and wheels 14 and 16 mounted adjacent one side 18 of the mine locomotive l and other wheels 20 and 22 mounted adjacent the other side 24 of locomotive 10. The wheels in the embodiment illustrated are recessed within the body of the locomotive l0 and are suitably connected to drive or propelling means (not shown). It should be understood, however, that the hereinafter described dual braking system is operable to be connected to mine locomotives with wheel arrangements other than those illustrated in the drawings and the relative position of the wheels and the number of wheels to which the brakes are applied is not critical to the hereinafter described braking apparatus. Wheels 14, 16, 20 and 22 are mounted on a pair of rails 26, one of which is illustrated in FIG. 2. The locomotive is preferably electrically propelled and has a power control device 28 in the operators compartment 12.

A mechanical braking apparatus for the locomotive is generally designated by the numeral 30 and includes a hand wheel 32 suitably mounted in the operator's compartment 12. A rod 34 has one end connected to the wheel 32 and is rotatable thereby. A transverse equalizer bar 38 has a bracket member 36 extending therefrom toward the rotatable hand wheel 32 and has an internally threaded bore or nut 35 in which the threaded end 37 of rod 34 is positioned. Rotation of hand wheel 32 and rod 34 moves the bracket 36 and equalizer bar longitudinally on the mine locomotive 10.

The equalizer bar 38 is suitably supported on a pair of longitudinally extending rail supports 40 and 42 for sliding movement thereon controlled by rotation of the hand wheel 32 and rod 34. The transverse equalizer bar has connector end portions 44 and 46 of reduced dimension that serve as connecting pins for the hereinafter described mechanical linkages to the brake shoes. The brake shoe assemblies generally designated by the numeral 45 include a pair of vertically extending brake levers 48 that are pivotally connected at their upper ends to links 50 by means of pins 51. The links 50 have elongated slots 52 therein in which the end portions 44 and 46 of equalizer bar 38 are positioned.

The brake shoe assemblies 45 further include a pair of hanger levers 54 and 56 that are pivotally connected to the body of the locomotive by means of pins 55 and 57. The lever 54 is pivotally connected at its lower end to a brake shoe 58 by pin 59. The hanger lever 56 is connected at an intermediate pivot connection to brake shoe 60 by a pin 61. The end of lever 56 is pivotally connected to a brake adjustment cylinder 62 by pin 63. The other end of brake adjustment cylinder 62 is pivotally connected by pin 64 to the lower end of brake lever 48. The brake lever 48 is also connected intermediate its end portions to the brake shoe 58. It will be apparent by the movement of brake levers 48 toward the operators compartment 12 that the brake shoes 58 and 60 are urged toward the respective wheels 14, 16, and 20, 22, and into frictional engagement therewith. The mechanical brake actuating mechanism 30 above described operates in the following manner. To apply the brakes to wheels 14, 16 and 20, 22 the hand wheel 32 is rotated in a preselected direction to rotate the rod 34 and threadedly move the threaded bore or nut 35 thereon to move the equalizer bar 38 toward the operators compartment 12. The equalizer bar 38 moves in the slotted overtravel slot 52 of link 50 and engages the link 50 to thus move link 50 toward the operators compartment 12. The link 50, in turn, through the pin connection 51, moves the brake levers 48 toward the operators compartment 12. The brake lever 48, in turn, moves the brake shoe 48 into frictional engagement with the respective wheel 14 or 20 and through the brake adjusting cylinder 62 also urges the brake shoe 60 into frictional engagement with the respective wheels 16 or 22 to engage the brake of the locomotive 10. To mechanically release the brake the hand wheel 32 is rotated in the opposite direction to move the equalizer bar 38 away from the operators compartment. The equlizer bar moves through the overtravel slot 52 in link 50 and thereafter moves the brake levers 48 in a clockwise direction as viewed in FIG. 2 to release the brake shoes 58 and 60. Suitable locking means may be provided to lock the brake in a fixed position as, for example when the vehicle is in a parked position.

The fluid actuated auxiliary braking apparatus is illustrated in FIGS. 1, 2 and 7 and is generally designated by the numeral 72. A hydraulic pump 74, preferably a manually operated pump that includes a metering valve within the pump housing, has a hand wheel 76 connected to the pump shaft 78. The pump is suitably mounted within the operators compartment 12 with the hand wheel 76 adjacent to the operator within the compartment 12. A suitable hydraulic pump for use in the fluid actuated auxiliary braking apparatus is sold under the trade name Orbitrol by the Char-Lynn Company of Minneapolis, Minn. The hydraulic pump has inlet and outlet ports 80 and 82 (FIG. 7) connected to a tank or reservoir 84 positioned within the operators compartment 12, preferably at an elevation above the pump 74. At this elevated location the hydraulic system is a self-bleeding system in that the air within the system will separate from the fluid in the tank 84. The pump 74 has a pair of cylinder ports and 92 connected by means of conduits 94 and 96 to a pair of piston cylinder assemblies generally designated by the numerals 98 and 100. The piston cylinder assemblies 98 and 100 are similar in construction and have a cylinder 102 with ports 104 and 106 on opposite sides of a piston within the cylinder (not shown). A piston rod 108 is connected to the piston within the cylinder and is arranged to move reciprocally with the piston in the cylinder 102. With this arrangement rotation of the hand wheel 76 in a first direction actuates the pump 74 to displace fluid therethrough and supply fluid through port 92 to conduit 96 and the rear ports 104 of both of the cylinders 102. The fluid supplied through conduit 96 displaces the pistons within the cylinders 102 to move the piston rods 108 outwardly from the cylinder 102. When the rotation of the hand wheel 76 is stopped, the piston rods 108 remain in an extended position. To retract the piston rods 108 the hand wheel 76 is rotated in the opposite direction to supply fluid through conduit 94 to the ports 106 of cylinders 102 and move the pistons rearwardly in the cylinders 102 and retract the rods 108. The fluid in the cylinders 102 displaced by the pistons therein flow through the other conduits through the pump 74 to the reservoir 84. With this arrangement there is a closed fluid system that includes the reservoir 84, the pair of piston cylinder assemblies 98 and 100, and the manually operated pump 74.

Now referring to FIGS. 1 and 2, the piston cylinder assemblies 98 and 100 are pivotally connected to brackets 112 by clevis type connections 110. The piston rods 108 have a forwardly extending arm portion 114 connected thereto. The arm portion 114 has an elongated overtravel slot 116 therein and a pin member 118 on brake levers 48 extend into the slot 116 of arm 114. To engage the brake shoes 58 and 60 to the respective wheels 14, 20, 16 and 22 by the hydraulically actuated brakinG apparatus 72, the hand wheel 76 is rotated in a preselected direction to supply fluid through conduit 96 to the ports 104 of cylinders 102.

The piston rods 108 are moved outwardly from the respective cylinders 102 and the arms 114 move forwardly toward the operators compartment 12 until the pin 118 moves in slot 116 and is engaged by arms 118. Further movement of the piston rod 108 pivots the brake levers 48 in a counterclockwise direction as viewed in FIG. 2 to engage the brake shoes 58 and 60 to the respective mine locomotive wheels. Continued rotation of the hand wheel 76 by means of fluid under pressure in conduit 96 further urges the brake shoes 58 and 60 into further frictional engagement with the respective mine locomotive wheels. To maintain a preselected braking force by the brake shoes, the hand wheel 76 is maintained in a fixed position. To release the brake shoes 58 and 60 the hand wheel 76 is rotated in the opposite direction to supply fluid through conduit 94 to the ports 106 of cylinders 102.

It should be noted that the brake assemblies 45 may be applied by either the mechanical braking apparatus 30 or the fluid actuated braking apparatus 72. The me chanical braking apparatus 30 is provided with overtravel means, i.e. slots 52 in links 50 to permit actuation of the brake assemblies 45 by the fluid actuated braking apparatus 72. The fluid actuated braking apparatus is also provided with an overtravel means, i.e. slot 116 in arm 114, to permit the brake assemblies 45 to be actuated by the mechanical braking apparatus 30. There are provided two independent braking systems for the mine locomotive 10, Le. the mechanical braking apparatus 30 and the fluid actuated braking apparatus 72. Both of the braking apparatus operate the same brake shoes in the brake assemblies 45. Thus, the fluid actuated braking apparatus 72 operates the same brake assemblies 45 as the mechanically actuated braking apparatus 30. It is preferred that the fluid actuated braking apparatus 72 be normally used as a service brake during the operation of the mine locomotive because of its ease in operation and the mechanically actuated braking apparatus 30 be used for parking the locomotive land for emergency use. The overtravel means, that is the slotted links 50 and slotted arm 114 permit each system, i.e. the mechanical braking system 30 and fluid actuated braking system 72, to have an unobstructcd travel through the full range.

Although, as illustrated in FIGS. 1 and 2, a pair of piston cylinder assemblies 98 and 100 are connected to the brake levers 48, it should be understood that the fluid actuated braking apparatus may include a single piston cylinder assembly directly connected to the equalizer bar, as illustrated in FIGS. 3 and 4 or a pair of piston cylinder assemblies connected to separate brake levers for the brake assemblies 45 or pairs of piston cylinder assemblies could be connected to the equalizer bar rather than a single piston cylinder assembly as illustrated in FIGS. 3 and 4.

Referring to FIGS. 3 and 4, the embodiment where a single piston cylinder assembly is connected to the equlizer bar along the longitudinal axis of the vehicle is illustrated. Since the embodiments in FIGS. 3, 4, 5 and 6 contain many of the components previously described in reference to FIGS. 1 and 2, similar numerals will be employed to designate similar parts. Further, in FIGS. 3 and 5 the details of the link connection between the equalizer bar and the brake levers have been omitted for clarity.

Referring to FIGS. 3 and 4, there is illustrated a fragmentary view of the mine locomotive 10 in which the rod 34 has its end portion threadedly secured in a bore of an arm member 152. The equalizer 38 has a forwardly extending bracket 154 with an upwardly extending pin member 156. The arm 152 has an elongated slot 158 in which the pin 156 is positioned. With this arrangement, the overtravel for the mechanical braking apparatus 30 is provided by means of the slot 158.

A piston cylinder assembly 160 has a piston 162 connected to a transverse support member 164 by a clevis 166. The piston 162 extends forwardly and has a piston rod 168 connected to a rearwardly extending bracket 170 on the equalizer bar 38. The piston rod 168 is positioned in a hollow rod 172 to permit overtravel of the fluid actauted braking apparatus 72 when the mechanical braking apparatus 30 is employed to actuate the brake assemblies 45. This provides a built-in overtravel device within the piston cylinder 160 providing for a minimum length piston that can be positioned in relatively confined areas. To actuate the mechanical brake actuating apparatus 30, the hand wheel 32 is rotated as previously described to move the arm member 152 until the pin 156 on bracket 154 engages at 152. Thereafter, further rotation moves the equalizer bar 38 and through the linkages previously described in reference to FIGS. 1 and 2, pivots the brake levers 48 in a counterclockwise direction to engage the brake shoes 58 and 60 to the respective locomotive wheels. During movement of the equalizer bar 38 by the hand wheel 32 and rod 34, the piston rod 168 moves longitudinally in the hollow rod 172 to provide the desired overtravel in the fluid actuated braking apparatus 72. To actuate the brake assemblies 45 with the fluid actuated braking apparatus 72 illustrated in FIGS. 3 and 4, fluid is supplied to the rear of cylinder 160 and moves both the hollow rod 172 and rod 168 toward the operators compartment 12 to thus move the equalizer bar 38 and the brake levers 48 in a counterclockwise direction. Overtravel for the mechanical braking apparatus 30 is provided by the pin 156 in slot I58.

Referring to FIGS. 5 and 6, there is illustrated another embodiment of the fluid actuated braking apparatus 72 that includes a pair of piston cylinder assemblies 200 and 202 with the rear end of pistons 204 and 206 connected to brackets 208 and 210 by clevis connections 212 and 214. The hollow tube type piston rods, substantially the same as previously described in reference to FIGS. 3 and 4 and designated by the numerals 216 and 218, are connected to separate brake levers 220. The brake levers 220 are pivotally connected intermediate their end portion to the brake shoe 60 by a pin connection 222. The ends of brake levers 220 are pivotally connected to the brake adjusting cylinder 62. The depending hanger link or lever 56 in this embodiment is pivotally connected to the brake shoe 60.

With this arrangement the brakes are applied by means of the fluid actuated braking apparatus 72 by supplying fluid to the front of the cylinders 200 and 202 to move the piston rods 216 and 218 outwardly and pivot the brake levers 220 in a clockwise direction to move the brake shoes 58 and 60 into frictional engagement with the respective locomotive wheels. The mechanical braking apparatus 34 is not illustrated in detail in FIGS. 5 and 6 and may be similar to the mechanical braking apparatus 30 illustrated in FIGS. 1 and 2 in which the equalizer bar 38 is connected by means of the rod 34 through brackets 36 so that rotation of hand wheel 32 moves the equalizer bar longitudinally toward the operators compartment and pivots the brake lever 48 in a counterclockwise direction to apply the brake shoes 58 and 60 to the respective wheels of the locomotlve.

According to the provisions of the patent statutes, l have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A dual braking system for mine locomotives comprising,

an equalizer bar extending transversely across the body of a mine locomotive, said equalizer bar having end portions terminating adjacent to wheels mounted on the sides of said mine locomotive body,

brake shoe assemblies including brake shoes positioned adjacent to said wheels,

a pair of brake levers pivotally connected to said brake shoe assemblies, said pair of brake levers operable to pivot in one direction and move said brake shoes into frictional engagement with said wheels,

links connecting said pair of brake levers to said equalizer bar end portions,

mechanical brake actuating means operable to mechanically move said equalizer bar through said links to pivot said pair of brake levers,

fluid actuated brake actuating means including a piston cylinder assembly connected to said brake assemblies and operable upon actuation to move said brake shoes into frictional engagement with said wheels,

said fluid actuated brake actuating means including a manually actuated fluid pump and a fluid reservoir,

conduit means connecting said fluid reservoir to said pump and providing a closed circuit therebetween,

a pair of conduits connecting said pump to a cylinder of a piston cylinder assembly on opposite sides of said piston to provide a closed circuit therebetween so that upon manual actuation of said pump fluid is supplied through one of said conduits to said cylinder, and

overtravel means for said mechanical brake actuating means and said fluid actuating means, said overtravel means operable to permit either said mechanical brake actuating means or said fluid actuated brake actuating means to frictionally engage said brake shoes to said wheels.

2. A dual braking system as set forth in claim 1 which includes,

means connecting said piston cylinder means to said equalizer bar.

3. A dual braking system for mine locomotives as set forth in claim 1 in which said piston cylinder means includes,

a pair of piston cylinder assemblies connected at one end to said locomotive body and at the other end to said respective brake levers.

4. A dual braking system for mine locomotives as set forth in claim 1 in which said piston cylinder means includes,

a piston cylinder assembly connected at one end to said locomotive body and at the other end to said equalizer bar along the longitudinal axis of said locomotive body.

5. A dual braking system for mine locomotives as set forth in claim 1 which includes,

a second pair of brake levers pivotally connected to said brake shoe assemblies, said second pair of brake levers operable to pivot in one direction and move said brake shoes into frictional engagement with said wheels,

said piston cylinder means including a pair of piston cylinder assemblies connected at one end to said locomotive body and at the other end to said respective second brake levers.

6. A dual braking system for mine locomotives as set forth in claim 1 in which said overtravel means for said mechanical actuating means includes,

an elongated slot in each of said links and pin means on said equalizer bar end portions extending into said respective slots in said links,

said equalizer bar pin means arranged to move in said elongated slots upon actuation of said fluid brake actuating means to move said brake shoes into frictional engagement with said wheels.

7. A dual braking system for mine locomotives as set forth in claim 3 in which said overtravel means for said fluid actuated brake actuating means includes,

an arm member connected to one end of said piston cylinder assembly, said arm member having an elongated slot therein,

pin means on said pair of brake levers,

said pin means positioned in said respective elongated slots and arranged to move in said elongated slots upon actuation of said mechanical brake actuating means to move said brake shoes into frictional engagement with said wheels.

8. A dual braking system for mine locomotives as set forth in claim 1 in which said overtravel means for said fluid actuated brake actuating means includes,

a piston cylinder assembly,

a piston rod telescopically positioned in a hollow rod, said piston rod connected to said equalizer bar and operable upon movement of said equalizer bar by said mechanical brake actuating means to move longitudinally relative to said hollow rod.

9. Auxiliary braking apparatus for a mine locomotive comprising,

a manually operable fluid pump,

a fluid reservoir,

a pair of conduits connecting said fluid reservoir to said manually operable fluid pump,

a piston cylinder assembly including a cylinder with ports on opposite sides of a piston,

other conduit means including a second pair of conduits connecting said manually operable pump to said ports in said cylinder to form a closed fluid circuit between said piston cylinder assembly and said manually operable fluid pump,

said manually operable fluid pump operable upon actuation to supply fluid through one of said second pair of conduits to extend or retract said piston in said piston cylinder assembly, and

said piston cylinder assembly operable to be connected to a portion of a mechanical brake actuating means so that upon actuation of said manually operable fluid pump said piston cylinder assembly actuates the brakes connected to said mechanical actuating means. 

1. A dual braking system for mine locomotives comprising, an equalizer bar extending transversely across the body of a mine locomotive, said equalizer bar having end portions terminating adjacent to wheels mounted on the sides of said mine locomotive body, brake shoe assemblies including brake shoes positioned adjacent to said wheels, a pair of brake levers pivotally connected to said brake shoe assemblies, said pair of brake levers operable to pivot in one direction and move said brake shoes into frictional engagement with said wheels, links connecting said pair of brake levers to said equalizer bar end portions, mechanical brake actuating means operable to mechanically move said equalizer bar through said links to pivot said pair of brake levers, fluid actuated brake actuating means including a piston cylinder assembly connected to said brake assemblies and operable upon actuation to move said brake shoes into frictional engagement with said wheels, said fluid actuated brake actuating means including a manually actuated fluid pump and a fluid reservoir, conduit means connecting said fluid reservoir to said pump and providing a closed circuit therebetween, a pair of conduits connecting said pump to a cylinder of a piston cylinder assembly on opposite sides of said piston to provide a closed circuit therebetween so that upon manual actuation of said pump fluid is supplied through one of said conduits to said cylinder, and overtravel means for said mechanical brake actuating means and said fluid actuating means, said overtravel means operable to permit either said mechanical brake actuating means or said fluid actuated brake actuating means to frictionally engage said brake shoes to said wheels.
 2. A dual braking system as set forth in claim 1 which includes, means connecting said piston cylinder means to said equalizer bar.
 3. A dual braking system for mine locomotives as set forth in claim 1 in which said piston cylinder means includes, a pair of piston cylinder assemblies connected at one end to said locomotive body and at the other end to said respective brake levers.
 4. A dual braking system for mine locomotives as set forth in claim 1 in which said piston cylinder means includes, a piston cylinder assembly connected at one end to said locomotive body and at the other end to said equalizer bar along the longitudinal axis of said locomotive body.
 5. A dual braking system for mine locomotives as set forth in claim 1 which includes, a second pair of brake levers pivotally connected to said brake shoe assemblies, said sEcond pair of brake levers operable to pivot in one direction and move said brake shoes into frictional engagement with said wheels, said piston cylinder means including a pair of piston cylinder assemblies connected at one end to said locomotive body and at the other end to said respective second brake levers.
 6. A dual braking system for mine locomotives as set forth in claim 1 in which said overtravel means for said mechanical actuating means includes, an elongated slot in each of said links and pin means on said equalizer bar end portions extending into said respective slots in said links, said equalizer bar pin means arranged to move in said elongated slots upon actuation of said fluid brake actuating means to move said brake shoes into frictional engagement with said wheels.
 7. A dual braking system for mine locomotives as set forth in claim 3 in which said overtravel means for said fluid actuated brake actuating means includes, an arm member connected to one end of said piston cylinder assembly, said arm member having an elongated slot therein, pin means on said pair of brake levers, said pin means positioned in said respective elongated slots and arranged to move in said elongated slots upon actuation of said mechanical brake actuating means to move said brake shoes into frictional engagement with said wheels.
 8. A dual braking system for mine locomotives as set forth in claim 1 in which said overtravel means for said fluid actuated brake actuating means includes, a piston cylinder assembly, a piston rod telescopically positioned in a hollow rod, said piston rod connected to said equalizer bar and operable upon movement of said equalizer bar by said mechanical brake actuating means to move longitudinally relative to said hollow rod.
 9. Auxiliary braking apparatus for a mine locomotive comprising, a manually operable fluid pump, a fluid reservoir, a pair of conduits connecting said fluid reservoir to said manually operable fluid pump, a piston cylinder assembly including a cylinder with ports on opposite sides of a piston, other conduit means including a second pair of conduits connecting said manually operable pump to said ports in said cylinder to form a closed fluid circuit between said piston cylinder assembly and said manually operable fluid pump, said manually operable fluid pump operable upon actuation to supply fluid through one of said second pair of conduits to extend or retract said piston in said piston cylinder assembly, and said piston cylinder assembly operable to be connected to a portion of a mechanical brake actuating means so that upon actuation of said manually operable fluid pump said piston cylinder assembly actuates the brakes connected to said mechanical actuating means. 